Apparatus and method for the optical characterization of the structure and composition of a light scattering sample

ABSTRACT

Apparatus for the optical characterization of the internal structure and/or composition of a spatially extended, scattering sample comprising an arrangement of one or several light sources and one or several light detectors and a displacement sensor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Subject matter of the invention is a method for the opticalcharacterization of the internal structure and/or composition of aspatially extended, light scattering sample with the aid of anarrangement consisting of one or several light sources, one or severallight detectors, and an apparatus suitable therefor.

2. Discussion of the Related Art

In the field of medical diagnostics, efforts have been made to make useof the internal structures of bodies to recognize diseases. Thisdevelopment began with the exposure of an object to light of a selectedwavelength or white light and recording the intensity of the reflectedlight (Non-invasive methods for the quantification of skin functions; P.J. Frosch and A. M. Klingman (ed.), Springer Verlag Berlin/Heidelberg,1993, pages 3 to 24 and 25 to 41). A drawback of this method is that itonly allows the detection of surface properties as the information isdetermined by the absorptive or reflective properties of the surface.Another drawback of the method is the poor reproducibility in aquantitative evaluation.

Even scanning devices used to read in a page of text only scan thesurface since the light, which is measured and reflected by light sourceand receiver essentially at the surface due to continuous exposure, mustnot or cannot penetrate the paper.

The basis for sonographic methods is to distinguish between differentstructures, e.g. different types of tissue, based on the differentreflection factors for sonic waves; said reflection factors beingproportional to the acoustic impedance (I. Krestel (ed.), BildgebendeSysteme fur die medizinische Diagnostik; Siemens AG, Berlin, Munchen,2nd edition 1988, page 183 et seq.). Sonographic methods can be used toobtain information from the interior of a sample, but they are entirelydependent on the mechanical properties (density). This means that it ispossible to differentiate and represent only structures with greatlyvarying acoustic impedances. When different soft tissue parts areanalyzed, the differences in the acoustic impedance and/or thereflection factor are very small and show either none or only very weakcontrasts.

Due to the optical properties of the tissue (scattering and absorptioncoefficient), the use of light with wavelengths in the near infra-redrange (NIR) allows in particular in the field of in-vivo analytics thepenetration of thicker tissue areas (some millimeters up to fewcentimeters) without damage (as is the case with X-rays). In currentlyknown methods various theories are used where the photon path must bemathematically traced back to generate an image based on the measuredlight intensities; this is accomplished either by the use of measuringmethods with a high time resolution (in the ps range) and/or withconsiderable calculation effort. The measuring apparatus used in thesemethods generally comprises a high performance, ultra-short pulsedlaser, a complex optical unit for laterally scanning the sample surface,and an ultra-fast detector. Possible lasers are, e.g. mode-coupled gasion laser (Ar, Kr) which synchronously pump dye lasers. Particularlysuitable for the detection are streak cameras, microchannelphotomultipliers, or Kerr-Shutter (L. Wang et al.: Ballistic Imaging ofBiomedical Samples using ps optical Kerrgate; SPIE Vol. 1431, TimeResolved Spectroscopy and Imaging of Tissues (1991), page 97 ff.).

Both handling and costs restrict the use of these apparatus to highlyqualified and highly specialized optical laboratories. Equivalentsemi-conductor components which can be used for the same type ofmeasurement and allow a necessary degree of miniaturization arepresently not available and/or a future availability is not yet insight. The instrumental difficulties are further complicated by theproblem of image reconstruction. Since there are countless ways for thephotons to travel from the light source to the detectors, it is notpossible to give one unique reconstruction algorithm, as is possible incomputer tomography, for example. Although first practical attempts atsolving the problem have been made (S. R. Arridge et al.; New resultsfor the development of infra-red absorption imaging; Proceedings ofSPIE--The International Society of Optical Engineering, Vol. 1245, pages92--103), a method for a successful reconstruction has not yet beenshown. Moreover, owing to the computing times involved, these methodsare not suitable for use in clinical diagnostics.

EP-A 0 387 793 describes a sensor that is placed on a skin section togenerate an optical image of the tissue beneath it. However, thisapparatus is not suitable for examining larger areas of the body as thiswould require a very large number of detectors. Moreover, the opticalresolution of the generated image is not satisfactory.

DE-A-4341063 describes a method for determining density distributions,wherein the light passing through the tissue is evaluated with respectto the phase and amplitude of high-frequency modulated radiation.

SUMMARY OF THE INVENTION

It was, hence, an object of the present invention to provide anapparatus and/or method that is also suitable to detect the internalstructure of light scattering samples in a high local resolution.

Subject matter of the invention is, hence, an apparatus or device forthe optical characterization of internal structures and/or compositionsof a light scattering sample. The invention comprises an arrangement ofone or several light sources and one or several light detectors. Thearrangement also comprises a diplacement sensor. Another subject matterof the invention is a method for the optical characterization of thesestructures.

An apparatus for the optical characterization is an instrument thatgenerates a characterization by emitting light from a light source anddetecting the light reflected by the sample on a detector. In accordancewith the invention, said apparatus may comprise one or several lightsources. Moreover, it is preferred that the apparatus comprise severallight detectors.

An optical characterization method includes all measurements that detecta certain property of light which is affected by the internal structureof the sample. This includes, for example, measuring the intensity(weakening the light intensity by absorption and scattering, e.g.corresponding to PCT/DE 93/01058), measuring the degree of polarizationof the light (depolarizing light that has been emitted as polarizedlight by means of scattering processes) or the traveling times ofphotons (e.g. corresponding to DE-A-43 37 570).

A spatially extended sample is a sample with a two-dimensional surfacewhose internal structure is inhomogeneous in 3 dimensions. It ispreferred to have samples with a minimum of 1 cm in length, 1 cm inwidth, particularly preferred are samples of 2 to 15 cm in length and 2to 5 cm in width.

To allow the emitted light to travel through the sample to the detectorwithout direct cross talk of the light source, the sample must scatterthe arriving light. In this case, the primary light can penetrate thesample through a boundary layer which surrounds the sample, thenpropagate in the sample along a light path to emerge again from thesample as a secondary light through a boundary layer that is away fromthe first boundary layer. The multiple light scatterings described inPCT/DE 93/01058 occur on the light path.

The scattering can occur through the particles contained in the sample,but also as a consequence of other internal structures, such as cellwalls. This property of a sample is met in particular by human andanimal tissue, especially skin and tissue layers found underneath,preferably up to a depth of approximately 25 mm.

The light source is selected such that it emits light with a knownintensity depending on measurement methods selected or a knownpolarization degree or a known intensity modulation of known phasemodulations. The light must also satisfy the aforementioned penetrationconditions and be subject to scattering by the sample. In order todetermine the optimal wavelength, the expert in the field proceeds asfollows:

For the preferred processing of absorbing structures such as bloodvessels, wavelengths are selected where the absorbance coefficient ofthe structure in question is great with respect to the environment, i.e.resulting in a high contrast. A wavelength of approx. 650 nm has provenwell for the detection of blood, for example.

For the preferred processing of scattering structures, a wavelength isselected with no or only small specific absorption ranges that couldfalsify the result as a decrease in the intensity could be a result ofhighly scattering structures in the light path or be caused byabsorption.

For the examination of objects, wavelengths in the ultraviolet visibleand infra-red range between 200 and 10000 nm are suitable.

Suitable wavelengths for the examination of human skin are those in therange between 400 and 2500 nm. Particularly preferred wavelengths arethose in the range between 400 and 1300 nm. Light sources to generate alight of such a wavelength are known to the expert. Particularlysuitable sources are laser diodes or LEDs as they are so small thatseveral light sources can be arranged on the relatively small surface ofthe apparatus.

Particularly suitable light detectors are photodiodes or CCDs as theycan be arranged in a narrow design.

A displacement sensor is a component which traces the path covered onthe surface of the sample when the apparatus is in motion and then feedsthis information to a control unit. Such displacement sensors areprincipally known to the expert.

Suitable instruments are mechanical instruments that work with angleencoding. When linear displacements are to be sensed, drum-type sensorsare preferred. If a non-linear displacement is to be sensed, sphericalsensors as they are known from a mouse for controlling a PC aresuitable. These displacement sensors are used to assign each valuemeasured at a light detector to a certain measuring site.

In a preferred manner, an arrangement of the invention for a lineardetection has at least two drums which are located before and after thelight sources and the light detectors in direction of movement. On thesurfaces, these drums are provided with a material to prevent sliding ofthe drum on the sample surface. In a preferred manner, the drums have arubber surface. Moreover, when elastic samples, e.g. tissue, are to beanalyzed, it is preferred that the surface of the drums extend 0.1 to 5mm, particularly preferred 0.5 to 2 mm, over the surface of theapparatus facing the sample, said surface containing the light sourcesand the light detectors. This distance ensures that there is no spaceleft between the surface of the apparatus and the surface of the samplewhen the apparatus is pressed onto the human skin. In this arrangement,interferences resulting from the reflection of the light emitted on tothe surface of skin and/or from radiation directly emerging from a lightsensor on to a detector are avoided as best as possible.

The assignment of the measured values (intensity to site of measurement)is carried out in an electronic evaluation unit. The values can bestored in a memory unit and be called up, if necessary. An intensityprofile can then be established for each pair of light source/lightdetector based on the total of all measured values for the measurementsites located on the path covered. If several pairs of lightsource/light detectors are evaluated, light detectors that are notlocated on the same path generate additional intensity profiles whichdescribe the inner structure of the sample between light source andlight detectors. The use of numerous large detectors, therefore,produces a 3-dimensional picture if the intensity is plotted independency on the covered path and the site of detection.

In addition to mechanical displacement sensors, it is also possible toemploy optical displacement sensing methods or mathematical methods.

By applying a regular bright/dark pattern with known dimensions on thesample, it is possible to clearly identify the site by measuring thebright and dark zones comparable to a barcode reader. This can beachieved either by using additional detectors located outside the actualmeasuring field, or the pattern can be recorded directly with ameasurement provided said pattern is applied directly on the sample orby means of a transparent carrier for the wavelength.

A mathematical method of sensing the displacement is the use of severalidentical measuring pairs. They are arranged such that they cover thesame site when the apparatus is moved in a given direction. They, hence,measure the same intensity profile but at different times and independency upon the speed of movement. With a given distance betweenthese two measurement pairs, the speed and, hence, the site can bemeasured while the time is known by establishing a time correlationbetween these two curves.

In the apparatus of the invention, the geometry of the arrangement oflight sources, light detectors and displacement of sensor during themeasurement is preferably constant. Principally, the arrangement cancomprise only one single light source with a corresponding lightdetector so that an intensity profile I can be generated as a functionof the site as stated above. In a second variant, only one light sourcebut several detectors are used. Said detectors are located either atdifferent distances to the light source and/or different angles betweenlight source/detector and direction of movement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the present invention;

FIG. 2 is a block diagram of the structural elements of the invention;

FIG. 3 describes a scattering test object for the present invention;

FIG. 4 illustrates a one-dimensional intensity profile of the testobject of FIG. 3;

FIG. 5 illustrates a two-dimensional intensity profile of the same testobject;

FIG. 6 illustrates variations of light source/detector arrangementsaccording to the present invention;

FIG. 7 illustrates a two-dimensional representation of an intensityprofile utilizing an apparatus according to the invention;

FIG. 8 illustrates various intensity/distance relationships;

FIG. 9 illustrates a scattering block used in a method according to thepresent invention;

FIGS. 10-13 illustrate intensity/path curves, signal development, andintensity profiles;

FIG. 14 illustrates an intensity profile showing damage to connectivetissue; and

FIGS. 15 and 16 are two-dimensional intensity distributions of a skinportion in gray values.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the preferred case, the arrangement of the invention comprisesseveral light sources and several light detectors. In order to carry outa measurement, it is preferred to activate only one light source at agiven time. This source detects the amount of light arriving at onedetector or several detectors. If several light sources are activated atthe same time, it must be ensured that the amount of light detected byone detector is emitted essentially by one light source, said amountbeing preferably 90%, preferably more than 99%. This also applies to theinfluence of foreign light sources, e.g. daylight or other sources ofillumination. The activation times of the light source should thereforebe timed. With the activation timing being known, it is possible to havea better assignment of activated light source and detectors to be readduring this cycle time. During a measurement, it is preferred that thecycle times be identical and constant. The activation times, orinversely the pulse frequencies, depend on the desired maximum speed ofmovement, the local resolution in direction of movement as well as thenumber of light sources and detectors which must be switched on and readfor given speed of movement in the given local resolution in directionof movement. During manual operation, appropriate speeds of movementrange between 1 and 20 cm/s. When the apparatus of the invention is usedtogether with mechanical support means for controlling the movement(e.g. motors) it is possible and expedient to have significantly higheror lower speeds depending on the local resolution. During manualoperation, pulse frequencies, e.g. for 16 light sources and 16detectors, range between 10 MHz and 1 kHz, preferably between 1 MHz and20 kHz. The resulting resolutions in direction of movement are below 0.1mm, i.e. below the size of the structures in question.

In an advantageous embodiment, light sources and light detectors arearranged in pairs, with each pair consisting of one light source and onelight detector. The light sources and light detectors of each pair arelocated on an assumed line that is essentially perpendicular to thedirection of movement of the arrangement (cf. FIG. 1).

According to FIG. 1, the light sources are preferably activated atdifferent times and the amount of light arriving at a given detector isdetected. The activated light source and the detector associated with itform one pair.

In a preferred manner, the distance between light source and lightdetector of each pair and the angle between light source detector anddirection of movement are the same. For the preferred samples and lightcharacteristics, a distance d of 1 to 50 mm, particularly preferred 2.5to 20 mm, has proven to be advantageous.

Light source and light detector of each pair are preferably located atthe same boundary of the sample, i.e. the reflection is measured.However, as soon as two opposite boundaries of the sample areaccessible, it is also possible to measure the transmission wherebylight source and light detector are located on opposite boundaries ofthe sample. The terms transmission and reflection used with respect tothe diffuse characteristics of the secondary light must not beunderstood to mean that the secondary light emerges from the sample witha highly dominating preferred direction.

In the figures, the lengths and distances X and Y are indicated inmillimeters. The intensities I are given in relative units.

Arrangement 1 shown in FIG. 1 shows in addition to the light sources 2and light detectors 3 also two drums 4 of which at least one serves as adisplacement sensor. This arrangement is therefore suitable for sensingseveral linear intensity profiles corresponding to the paths covered bythe detectors in direction of movement 5.

In addition to this arrangement, the apparatus in accordance with theinvention also comprises additional components that are advantageous forits use. It must be taken into consideration that these components canbe connected to each other either in a rigid or flexible manner, butalso via communication pathways. To ensure proper functioning, theresulting one-piece or multi-piece apparatus should comprise anelectronic control unit for light sources and detectors, an amplifier, adisplay, a recorder or an analog-to-digital converter, and a computerfor further processing the generated data in addition to the describedarrangement of light sources, light detectors and displacement sensor.In a preferred manner, all the aforementioned components with theexception of arrangement 1 are included in a footed instrument whereasarrangement 1 comes as a relative small handy instrument. The connectionbetween these two elements can be accomplished either mechanically viaflexible cables or electromagnetic radiation.

FIG. 2 is a block diagram of the structure in accordance with theinvention.

FIG. 3 describes a test object made of a scattering material (thicknessapprox. 20 mm, made of Teflon) in which there are mechanicalinhomogeneities in the form of defined recesses (depth 4.5 mm (1) or 2.5mm (rest)) at different distances.

FIG. 4 shows a one-dimensional intensity profile I as a function of thesite. The profile was generated by measuring the test object describedin FIG. 2 with the aid of the apparatus in accordance with theinvention. The distances between light source and detector wereapproximately 7 mm.

FIG. 5 shows a two-dimensional intensity profile that was generated withthe same test object. The apparatus used to develop the profile of FIG.5 included fourteen sources and fourteen detectors corresponding toarrangement A in FIG. 6 with a distance d of 7 mm. Other quantities oflight sources and detectors could be used, and still be within thespirit and scope of the invention.

FIG. 6 shows three possible variants for arranging lightsources/detectors. In arrangement A, both light sources (2) and lightdetectors are arranged on an assumed line. The distance between the twolines is identified with the letter d. In arrangement B, an evaluationfor two different distances d1 and d2 is made possible in that a secondrow of light detectors is provided. The same effect can be achieved byusing two rows of light sources and only one row of light detectors(arrangement C).

FIG. 7 is a two-dimensional representation of the intensity as afunction of the covered paths and the light source/detector position. Itwas obtained on human skin with an apparatus according to FIG. 1. Thefigure shows the intensity profiles of 14 detectors over a path of 60mm. The location of a vein (low intensity, dark spots) can be clearlyidentified.

As the light property is measured in terms of reflection aftertraversing the sample, the two-dimensional intensity profile isdetermined by parameters which affect the optical properties of theobject to be examined.

The so measured intensity of profiles which first allow only a relativeassociation can be used to clearly determine the inner structure of agiven area in that the site of the start or the end of a measurement onthe sample is recorded. It is thus possible to associate the relativeintensity measurement with certain sites on the sample. Advantageously,an origin of coordinates is defined on the apparatus for the exactidentification of the various directions of movement. Advantageously,this is the position of the light sources or the detectors.

Another subject matter of the invention is a method for the opticalcharacterization of the inner structure and/or a composition of aspatially extended, scattering sample. The apparatus comprising one orseveral light sources and one or several light detectors is moved acrossthe spatially extended sample. The movement of the arrangementconsisting of light sources and light detectors is advantageouslyrecorded via a displacement sensor. During the movement of theapparatus, the light arriving at the light detectors is detected and thegenerated signal is recorded. In order to associate the measured signalswith given sites on the sample, the measured intensity is correlatedwith the covered path. This is advantageously done with the aid of acomputer. The resulting intensity profiles can be represented eithernumerically or graphically.

The distance d between light source and light detector also affects thepossible resolution accuracy. FIG. 8 shows examples of intensities forcases where the distance d is larger than the inner structure; where dis approximately the same as the inner structure; and where d is muchsmaller than the inner structure. In this case, the inner structure is agap in the surface of a sample across which the arrangement is moved. Byusing different wavelengths and/or light source/detector distances, itis possible to prefer certain penetration depths, and increase thespecificity for certain components. When vessels are examined, asuitable wavelength is one where hemoglobin shows an absorption. Partswith numerous vessels then show a higher absorption which leads to alower measured light intensity at the light source/detector pairs abovethe vessel.

FIGS. 9 to 13 show the method of the invention as used in anotherdetailed embodiment. A scattering block made of plastic was providedwith absorbing structures of different depths and filled with anabsorbing medium to simulate absorbing blood vessels in the tissue. Thebores have a diameter of 1 mm and are parallel to the surface at adistance of 2.8 and 5.0 mm to the surface, and at an approximate lengthof 20 mm (FIG. 9).

Because of the form of the intensity/path curves, it is possible toprovide data on the length, depth and shape of the structures. FIG. 10shows the intensity/path curve for a selected light source/detector pairwith a distance of 7 mm. FIG. 11 shows the signal development for thesame light source, however, for a detector at a distance of 14 mm. Thesignals at 25 mm and 50 mm of path traveled correspond to bores with adepth of 2.8 and 5.0 mm, respectively. The size and depth of theabsorbing bores can be concluded from the different forms of thesignals. Structures that are close to the surface shows deep signaldecrease for a small light source/detector distance, and the lowerstructure is shown as a relatively weak and broad signal decrease. FIGS.12 and 13 show the intensity over the entire width of the scanned areafor a distance of 7 mm and 14 mm, respectively, between light source anddetector.

FIG. 14 shows that the method of the invention is also suitable forin-vivo measurements. FIG. 14 shows the measurement of damage toconnective tissue caused by overstretching (striae). The plotted diagramshows the reflected intensity or a light source/detector distance of 7mm as a function of the path. Strip-like alterations of the skin runningperpendicularly to the scanning direction can be seen between 0 and 15mm path and after 100 mm. The path between 50 and 100 mm shows normaltissue. Instruments in accordance with the invention can be used forboth the documentation of such findings and their control duringtherapy. As opposed to a mere visual evaluation, the intensity profilesshown also allow an evaluation of the course and the extent of tissuealterations inside the skin in a non-invasive manner.

FIG. 15 shows that the method of the invention can also be used toevaluate the homogeneity of tissue. In order to determine the opticalproperties of the skin, it is important to evaluate the examined siteswith respect to homogeneity since it is not a defined site, but avaguely defined volume that is measured due to the scattering characterof the skin. The derived optical values are, hence, mean values of thisvolume. It is, therefore, necessary to know the homogeneity of thetissue area examined to exclude false mean values that may have beencaused by inhomogeneities.

FIGS. 15 and 16 show the measured two-dimensional intensity distributionof a skin portion in gray values. In FIG. 15, the light source detectordistance was 7 mm; in FIG. 16, the distance was 14 mm. The area of skinexamined can be further divided in areas of similar intensities byfurther processing the data, one possibility being the zone growthmethod. In this method, a freely selected intensity value of thetwo-dimensional data structure I(x,y) is in a first step compared to theadjacent value I(x+1, y+1), I(x, y+1), I(x-1, y+1), and so forth. Thoseadjacent values which fulfill a given comparison criterion, e.g. rangingwithin a certain value range together with the first point, form onearea. The result is a first area with similar intensity values. Todetermine further areas, another starting point outside the alreadydetermined area or zone must be determined and the above-describedcomparison procedure is repeated. As opposed to measurement on theboundary of the areas shown, it is advantageous to measure the opticalproperties within such defined areas. Moreover, a comparison betweenFIGS. 15 and 16 shows that when different light source detectordistances are present, the examined tissue has different homogeneousareas.

Another subject matter of the invention are advantageous applicationsand uses of the apparatus and the method of the invention. The followingare possible examples:

Determining a time-related alteration of a sample, e.g. before and aftersurgery or during the healing process. The reproducibility of theintensity profiles also allows long-term examinations, e.g. duringpathogenic alterations of the skin or controlling the size of skinalterations (moles, birthmarks). In addition, the method is alsosuitable to examine foreign bodies included in the skin.

Classification of different skin types. In this case, the use ofdiscriminance analyses for establishing different types and associatingindividual samples to these types is advantageous.

The good local resolution in direction of movement is particularlysuitable to derive values from the intensity/path profiles inmathematical operations to successfully identify certain skin areas. Itis, for example, possible to determine characteristic, periodicallyrepeated properties of the tissue types via Fourier transformation ofthe intensity profile for the individual tissue types followed by adiscriminance analysis.

Scanning of sites or homogeneity locally or in a time-related manner.Tissue, in particular human skin, is locally inhomogeneous because ofstructures therein or therebelow. Some parts of the body may be more orless suitable for diagnostic purposes. There are parts that are well orless well suited for a measurement, in particular in case of anon-invasive determination of analyte concentrations in certain tissueparts, e.g. in case of a non-invasive determination of the glucoseconcentration, according to PCT-DE 93/01058 or U.S. Pat. No. 5,028,787.With the present invention, well-suitable measurement sites can bedetermined and labeled. This is also advantageous if the non-invasivemeasurement instrument must be removed from the sample between twomeasurements and later be attached again. The method of the invention isalso suitable to determine the size and/or time-related changes tohomogeneous areas of the sample.

The above-described methods can also be applied to non-biologicalsamples. With the apparatus of the invention it is possible to examinematerial in scattering media without damage. This includes homogeneitytests for plastics and examining molded pieces with structures belowtheir surface.

List of Reference Numerals

(1) Arrangement in accordance with the invention

(2) Light sources

(3) Detectors

(4) Drums

(5) Direction of movement

(10) Graphical and/or numerical representation of the light intensity asa function of location

(11) Timing pulse generator

(12) Electronic data analyzer, correlation of path and light intensity

(13) Light sources and electronic drive unit

(14) Detectors and amplifier

(15) Path recording

We claim:
 1. An apparatus for in-vivo optical analysis of internalstructures of a specimen of light scattering tissue by moving saidapparatus relative to a surface of the specimen, said apparatuscomprising:at least one light irradiating means for irradiating primarylight into the surface of an in-vivo specimen; at least one lightdetecting means for detecting secondary light from the surface of thespecimen; and displacement sensor means for sensing a relative movementbetween the light irradiating means and the light detecting meansrelative to the surface of the specimen, said displacement sensor meanstracing a path on the surface of the specimen and sensing displacementwhen the apparatus is moved on the surface of the specimen; andevaluation means connected to said light irradiating means, said lightdetecting means, and said displacement sensor means, said evaluationmeans processing data from said light detecting means and saiddisplacement sensor means, and correlating the relative movement withsaid data from said light detecting means.
 2. An apparatus as recited inclaim 1, further comprising display means connected to said evaluationmeans, for displaying an optical image generated by the evaluation meansthereupon.
 3. An apparatus as recited in claim 1, wherein saiddisplacement sensor means is coupled to said light irradiating means andsaid light detecting means.
 4. An apparatus as recited in claim 1,wherein said evaluation means also generates an optical image from thedata which is processed from the light detecting means and the lightdisplacement sensor means.
 5. An apparatus as recited in claim 1,wherein said evaluation means generates a one-or-more dimensionalintensity profile from said data.
 6. An apparatus as recited in claim 1,wherein said evaluation means generates a classification of a specimentype based upon the data process from the light detecting means and thedisplacement sensor means.
 7. An apparatus as recited in claim 1, saidapparatus comprising a plurality of light irradiating means.
 8. Anapparatus as recited in claim 1, comprising a plurality of lightdetecting means.
 9. An apparatus as recited in claim 1, comprising aplurality of light irradiating means and a plurality of light detectingmeans, wherein each of said plurality of light irradiating means ispaired with a corresponding one of the plurality of light detectingmeans.
 10. An apparatus as recited in claim 9, wherein correspondinglight irradiating means and light detecting means are separated by asame distance as other corresponding light irradiation means and lightdetection means.
 11. An apparatus as recited in claim 10, wherein saidsame distance is between 0.5 mm and 100 mm.
 12. An apparatus accordingto claim 9, wherein said plurality of light irradiating means and saidplurality of light detecting means are disposed in a coplanarconfiguration.
 13. An apparatus as recited in claim 1, wherein saidlight detecting means detects light intensity.
 14. An apparatus asrecited in claim 1, wherein said light detecting means detects a degreeof polarization of the secondary light.
 15. An apparatus as recited inclaim 1, wherein said light detecting means detects a travel time ofphotons from the light irradiation means to the detecting means.
 16. Anapparatus according to claim 1, wherein said at least one lightirradiating means and said at least one light detecting means aredisposed in a coplanar configuration.
 17. A method for in-vivo opticalanalysis of internal structures of a specimen of light scatteringtissue, said method comprising the steps of:irradiating primary lightinto a surface of a scattering in-vivo specimen with a light irradiatingmeans; detecting secondary light emerging from the surface of thespecimen with a detecting means; displacing said light irradiating meansand said detection means relative to the surface of the specimen;sensing a displacement of said light irradiating means and said lightdetecting means with respect to the surface of the specimen with adisplacement sensor means, said displacement sensor means tracing a pathon the surface of the specimen and sensing displacement when thedisplacement sensor means is moved on the surface of the specimen;processing data from the light detecting means and the displacementsensor means; and correlating the data from the light detecting meansand the displacement sensor means.
 18. A method according to claim 17,comprising a further step of generating an optical image from thecorrelated data.
 19. A method according to claim 17, further comprisinga step of generating a one-or-more dimensional intensity profile of thespecimen based upon the correlated data.
 20. A method according to claim17, further comprising a step of classifying a sample type based uponthe correlated data.
 21. A method according to claim 17, furthercomprising a step of storing data from the light detecting means and thedisplacement sensor means prior to the correlation of the data.
 22. Amethod according to claim 17, wherein said step of irradiating primarylight includes controlling a timing of an irradiation cycle for thelight irradiation means.
 23. A method according to claim 17, whereinsaid step of irradiating primary light includes steps of irradiatinglight from a plurality of light irradiation means, with at least two ofsaid plurality of light irradiation means having different irradiationcycles.
 24. A method according to claim 17, wherein said step ofdetecting secondary light comprises a step of detecting secondary lightwhich is reflected from the specimen.
 25. A method according to claim17, wherein said step of irradiating primary light into the samplecomprises a step of irradiating light having a wavelength which isbetween 400 nm and 10,000 nm.
 26. A method according to claim 17,wherein said step of irradiating primary light comprises irradiatinglight from a plurality of light irradiating means, and wherein said stepof detecting light includes a step of detecting light with a pluralityof light detecting means, wherein each of the plurality of lightirradiating means is paired with a corresponding one of the plurality oflight detecting means, and wherein a distance between correspondinglight irradiating means and light detecting means is approximately asame size or smaller than a size of an inhomogeneity in the sample whichis to be measured.
 27. A method according to claim 17, wherein saidirradiating, detecting, and evaluating steps are repeated in order toevaluate time-related changes to the sample.
 28. A method according toclaim 17, wherein said step of detecting secondary light comprises adetection of intensity of the secondary light.
 29. A method according toclaim 17, wherein said step of detecting secondary light includes a stepof detecting a degree of polarization of the secondary light.
 30. Amethod according to claim 17, wherein said step of detecting thesecondary light comprises a step of detecting a travel time of photonsfrom the light irradiation means to the detecting means.